The secondary cells such as fuel cells, nickel-cadmium cells, nickel-hydrogen cells, lithium-ion cells, lead batteries etc. are used for power supplies of automobiles or portable electronic devices and home electric appliances such as cell-phones, laptop personal computers, and so on.
These cells each have a safety valve to automatically release a pressure to the external world when an internal pressure becomes excessively high.
For example, Japanese Unexamined Patent Publication No. JP 05-47363A discloses a sealed-type secondary cell comprising a curved space portion and a safety valve portion where the curved space portion communicates with a space stored with electrode plates at a part of a connection portion in the periphery of connected films where the electrode plates are sandwiched in between while the safety valve portion has a small opening or a slit that passes through from one film's outer surface to the other film's out surface. However, with the development of recent downsizing technique in battery cells and home electric appliances, there is a demand for smaller and simpler safety valves that can surely and safely work at a relatively low excessive pressure and release the excessive pressure to the external world.
Specifically in a case of fuel cells that use hydrogen as fuel where the internal pressure might become excessively high due to oversupply of hydrogen, overheating, overreaction and so on, it is desired to set up a high-precision safety valve that can automatically release an excessive pressure to the external world. Further, it is also desired to set up an inexpensive, mass-producible, homogenous, general-purpose compact-sized safety valve for electrolysis tanks of fuel cells or secondary cells, cases for portable electronic devices and their sealing components, air piping, storage containers for volatile chemicals or sparkling beverages.
Japanese Unexamined Patent Publication No. JP 10-118178A discloses a medical check valve comprising a concave portion dented like an inverted cone shape on the upper surface side, a convex portion on the lower surface side protruded in the same direction as that of the protrusion of the concave portion and a syringe-insertion opening formed so as to pass through the lowermost point of the concave portion. The medical check valve is used for reliable co-injection, with easy-to-use operation, of fluid medicines pre-filled in a syringe at the time of fluid infusion or blood transfusion. The medical check valve has a difficulty in providing a uniform insertion opening, without misalignment, at the lowermost point of the small concave portion for whole product lines. However, even when there are some misalignments, doctors and nurses strongly insert a syringe manually to widen the slit and then press a pusher of the syringe to co-inject the solution of the syringe, therefore improper operation of the valve can be prevented. However, this medical check valve cannot be used as an excessive pressure release valve for the fuel cells and the like, because the excessive pressure release valve of the fuel cells must work automatically and accurately to release the pressure toward the external world only when the internal pressure becomes excessively high.
On the other hand, Japanese Unexamined Patent Publication No. JP 2002-106766A discloses a compact-sized tube coupling mountable with one simple operation on an external fluid device, which comprises a joint body with a locking claw and an attaching portion to attach the joint body to a coupling opening of the external fluid device. Because this tube coupling is used for flowing of fluid, a release valve is not provided along a route of the fluid.